Changes between Version 21 and Version 22 of MMC

Timestamp:

02/23/2022 06:18:17 PM (2 years ago)

Author:

Tim Harvey

Comment:

added bus details

MMC

@@ -31 +31 @@
  * Dual-Data-Rate (DDR) (Note this is supported on microSD if the card/controller support UHS-I)
  * device is on-board and thus non removable
+
+=== eMMC bus
+The initial bus speed is started with 25MHz SDR mode and depending on the capabilities of the host and device can negotiate to higher rates:
+||= Mode         =||= Data Rate =||= IO voltage =||= Bus width =||= Frequency =||= Max data rate at 8bit bus =||
+|| Legacy         || Single      || 3/1.8/1.2V   || 1,4,8       || 0 - 26MHz   || 26MB/s ||
+|| High Speed SDR || Single      || 3/1.8/1.2V   || 1,4,8       || 0 - 52MHz   || 52MB/s ||
+|| High Speed DDR || Dual        || 3/1.8/1.2V   || 1,4,8       || 0 - 52MHz   || 104MB/s ||
+|| HS400          || Single      || 1.8/1.2V     || 4,8         || 0 - 200MHz  || 200MB/s ||
+|| HS400          || Dual        || 1.8/1.2V     || 4,8         || 0 - 200MHz  || 400MB/s ||
 
 
@@ -315 +324 @@
  * SDXC 64GB to 2TB
 
+=== MicroSD bus
+The initial SD bus speed of 12.5MB/s is the default mode defined by SD1.0. Later a 25MB/s High Speed Mode (HS) was defined by SD1.1. As higher performance levels were needed to support new and faster devices the SD association introduced faster bus interfaces: UHS-I, UHS-II, UHS-III, and SD Express. The bus speed is started with 25MHz SDR mode and depending on the capabilities of the host and device can negotiate to higher rates:
+||= Mode         =||= Data Rate =||= Max Frequency =||= Max data rate at 8bit bus =||
+|| Default Speed (DS) || Single  || 25MHz   || 12.5MB/s ||
+|| High Speed (HS)    || Single  || 50MHz   || 25MB/s ||
+|| UHS-I DDR50        || Dual    || 50MHz   || 50MB/s ||
+|| UHS-I SDR50        || Single  || 100MHz  || 50MB/s ||
+|| UHS-I SDR104       || Single  || 208MHz  || 104MB/s ||
+ * Note that UHS-I requires support for voltage switching I/O rail from 3.3V to 1.8V
+ * All modes start at DS and negotiate up if supported on both host and card
 
 === MicroSD References